1. Field of the Invention
The present invention relates to a pattern measurement method and a pattern measurement system, and especially relates to a method and system for measuring a pattern from a scanned image obtained by a scanning electron microscope.
2. Description of the Related Art
In a manufacturing process of a semiconductor, generally, a circuit pattern on a semiconductor integrated circuit is inspected. One of an inspection method of the circuit pattern is that using Computer Aided Design (CAD) data being design data of the circuit pattern, as a standard pattern. In this method, the circuit pattern is evaluated by comparing a scanned image of an actually formed pattern with the CAD data.
Japanese Patent Application Laid-Open (JP-A) No. 2001-338304 (corresponding to U.S. Pat. No. 6,868,175) and JP-A No. 2002-31525 (corresponding to US2002/0015518) disclose to perform edge detection for each of a pattern image of an inspection object and the standard pattern, and compares the detected edges to detect a variation amount of the pattern with respect to the design data. Also, JP-A No. 2006-234588 (corresponding to US2006/0193508) discloses a method of setting a standard position regarding positioning between the design pattern and an actual pattern image to detect the pattern variation amount in greater detail.
Recently, due to a minute pattern of the semiconductor integrated circuit, a proximity effect of light in a photolithography technique becomes problematic. The proximity effect of light is a phenomenon in which a shape of the actually formed pattern is different from a shape of a mask pattern, when exposing the pattern to transfer. This is because a diffraction effect of light occurs when a pattern width is minute.
In order to eliminate the proximity effect of light to obtain a desired pattern, the mask pattern is corrected. This is referred to as an optical proximity correction (OPC). In the OPC technology, a light intensity distribution of an image passing through the mask pattern and being reduced-projected on a wafer is calculated, or ruled to change mask pattern data. Thereby, the desired pattern just as the design data may be obtained on the wafer. In general, the mask pattern changed by the OPC technology is referred to as an OPC pattern, and a dimension of the OPC pattern is often measured in the manufacturing process of the mask.